Lateral spin valve reader with vertically-integrated two-dimensional semiconducting channel

ABSTRACT

A lateral spin valve reader includes a detector located proximate to a bearing surface of the reader, and a spin injector located away from the bearing surface. The lateral spin valve reader also includes a channel that extends from the detector to the spin injector. The channel includes a two-dimensional semiconducting layer that extends from the detector to the spin injector.

BACKGROUND

Data storage devices commonly have a recording head that includes a readtransducer that reads information from a data storage medium and a writetransducer that writes information to a data storage medium.

In magnetic data storage devices such as disc drives, a magnetoresistive(MR) sensor such as a Giant Magnetoresistive (GMR) sensor or a TunnelJunction Magnetoresistive (TMR) sensor has traditionally been employedas the read transducer to read a magnetic signal from the magneticmedia. The MR sensor has an electrical resistance that changes inresponse to an external magnetic field. This change in electricalresistance can be detected by processing circuitry in order to readmagnetic data from the adjacent magnetic media.

The ever increasing need for increased data storage necessitates everincreasing data density in magnetic data storage devices. One way toincrease data density is to decrease the size and spacing of magneticbits recorded on the media. The read sensor is generally sandwichedbetween a pair of magnetic shields, the spacing between which determinesthe bit length, also referred to as gap thickness. Sensors such as GMRor TMR sensors are constructed as a stack of layers all formed upon oneanother sandwiched between the magnetic shields. Accordingly, theability to reduce the spacing between shields with such a sensorstructure is limited.

SUMMARY

The present disclosure relates to a lateral spin valve reader thataddresses scaling challenges posed by greater data density requirements.The lateral spin valve reader includes a detector located proximate to abearing surface of the reader, and a spin injector located away from thebearing surface. The lateral spin valve reader also includes a channelthat extends from the detector to the spin injector. The channelincludes a two-dimensional semiconducting layer that extends from thedetector to the spin injector.

Other features and benefits that characterize embodiments of thedisclosure will be apparent upon reading the following detaileddescription and review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a data storage system.

FIG. 2 is a generalized functional block diagram of a data storagesystem.

FIG. 3A is a schematic diagram of a cross-section of one embodiment of arecording head that reads from and writes to a storage medium.

FIGS. 3B, 3C and 3D are schematic diagrams of cross-sections of otherembodiments of a recording head that reads from and writes to a storagemedium.

FIGS. 4A, 4B and 4C are graphs that illustrate properties of metalchannels that may be employed in lateral spin valve readers.

FIG. 5A is a schematic perspective view of a lateral spin valve readerin accordance with one embodiment.

FIG. 5B is a cross-sectional view of the lateral spin valve reader ofFIG. 5A.

FIG. 6 is a simplified flow diagram of a method embodiment.

FIGS. 7A-7HH are schematic diagrams of reader layers that collectivelyillustrate formation of a lateral spin valve reader in accordance withone embodiment.

FIGS. 8A and 8B are schematic diagrams that illustrate steps in theformation of a portion of a lateral spin valve reader in accordance withanother embodiment.

FIG. 9 is a schematic diagram that illustrates a step in the formationof a lateral spin valve reader in accordance with yet anotherembodiment.

FIGS. 10A, 10B and 10C are schematic diagrams of cross-sections oflateral spin valve readers with different lead terminal configurations.

FIGS. 11A and 11B are diagrammatic illustrations of cross-sections ofmulti-sensor readers in accordance with different embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Magnetic reader embodiments described below relate to lateral spin valve(LSV) readers that include a spin injector, a detector and a channelextending from the spin injector to the detector. The spin injectorinjects electron spins into the channel, which transports the spins tothe detector. At the detector, the spins aid in detecting bits stored ona magnetic data storage medium. The LSV reader is sandwiched between apair of magnetic shields. In different embodiments, the channel of theLSV reader includes a two-dimensional semiconducting layer to provide adrastic reduction in shield-to-shield spacing (SSS) in the reader. Priorto providing additional details regarding the different embodiments, adescription of an illustrative operating environment is provided below.

FIGS. 1 and 2 together show an illustrative operating environment inwhich certain specific embodiments disclosed herein may be incorporated.The operating environment shown in FIGS. 1 and 2 is for illustrationpurposes only. Embodiments of the present disclosure are not limited toany particular operating environment such as the operating environmentshown in FIGS. 1 and 2. Embodiments of the present disclosure areillustratively practiced within any number of different types ofoperating environments.

FIG. 1 is a perspective view of a hard disc drive 100. Hard disc drivesare a common type of data storage system. While embodiments of thisdisclosure are described in terms of disc drives, other types of datastorage systems should be considered within the scope of the presentdisclosure. The same reference numerals are used in different figuresfor same or similar elements.

Disc drive 100 includes a data storage medium (for example, a magneticdisc) 110. Those skilled in the art will recognize that disc drive 100can contain a single disc or multiple discs. Medium 110 is mounted on aspindle motor assembly 115 that facilitates rotation of the medium abouta central axis. An illustrative direction of rotation is shown by arrow117. Each disc surface has an associated recording head 120 that carriesa read transducer and a write transducer for communication with thesurface of the disc. Each head 120 is supported by a head gimbalassembly 125. Each head gimbal assembly (HGA) 125 illustrativelyincludes a suspension and a HGA circuit. Each HGA circuit provideselectrical pathways between a recording head and associated hard discdrive electrical components including preamplifiers, controllers,printed circuit boards, or other components. Each suspensionmechanically supports an HGA circuit and a recording head 120, andtransfers motion from actuator arm 130 to recording head 120. Eachactuator arm 130 is rotated about a shaft by a voice coil motor assembly140. As voice coil motor assembly 140 rotates actuator arm 130, head 120moves in an arc between a disc inner diameter 145 and a disc outerdiameter 150 and may be positioned over a desired track such as 152 toread and/or write data.

FIG. 2 is a generalized block diagram of illustrative control circuitryfor the device shown in FIG. 1. The control circuitry includes aprocessor or controller 202 that directs or manages the high leveloperations of device 100. An interface circuit 204 facilitatescommunication between device 100 and a host device 250. A read/writechannel 206 operates in conjunction with a preamplifier/driver circuit(preamp) 208 to write data to and to read data from a data storagemedium such as medium 110 in FIG. 1. Preamp 208 also optionally acts asa power supply to electrical components included in a recording headsuch as a read transducer, a write transducer, heaters, etc. Preamp 208is illustratively electrically connected to recording head 120 through aHGA circuit that is connected to preamp 208 and to one or more recordinghead 120 electrical connection points. A servo circuit 210 providesclosed loop positional control for voice coil motor 140 that positionsrecording head 120.

FIG. 3A is a schematic diagram showing a cross-sectional view ofportions of a recording head 300 and a data storage medium 350 takenalong a plane substantially normal to a plane of a bearing surface (forexample, an air bearing surface (ABS)) 302 of recording head 300. Therecording head elements shown in FIG. 3A are illustratively included ina recording head such as recording head 120 in FIGS. 1 and 2. Medium 350is illustratively a data storage medium such as medium 110 in FIG. 1.Those skilled in the art will recognize that recording heads andrecording media commonly include other components. Embodiments of thepresent disclosure are not limited to any particular recording heads ormedia. Embodiments of the present disclosure may be practiced indifferent types of recording heads and media.

Recording head 300 includes a write pole 305, a magnetization coil 310,a return pole 315, a top shield 318, a read transducer 320, a bottomshield 322 and a wafer overcoat 336. Storage medium 350 includes arecording layer 355 and an underlayer 360. Storage medium 350 rotates inthe direction shown by arrow 365. Arrow 365 is illustratively adirection of rotation such as arrow 117 in FIG. 1.

In an embodiment, electric current is passed through coil 310 togenerate a magnetic field. The magnetic field passes from write pole305, through recording layer 355, into underlayer 360, and across toreturn pole 315. The magnetic field illustratively records amagnetization pattern 370 in recording layer 355. Read transducer 320senses or detects magnetization patterns in recording layer 355, and isused in retrieving information previously recorded to layer 355.

In the embodiment shown in FIG. 3A, read transducer 320 is a LSV reader.LSV reader 320 includes a spin injector 324, a detector 326 and achannel 328 that extends from spin injector 324 to detector 326. Aninsulator 334 may be disposed around the channel 328. Insulation layer334 between bottom shield 322 and channel 328 is substantially thinnerthan injector 324 in a region proximate to the bearing surface 302.

The spin injector 324 may include an electrically conductive, magneticlayer (not separately shown in FIG. 3A) that has a magnetization that ispinned in a direction (preferably perpendicular to the bearing surface).Pinning of the magnetization of the pinned magnetic layer may beachieved by, for example, exchange coupling with a layer ofanti-ferromagnetic material (not separately shown in FIG. 3A).

The detector 326 may include a magnetic, electrically conductive layerhaving a magnetization that is free to move in response to a magneticfield, and can therefore be referred to herein as a free layer (FL).Detector 326 may be separated from channel 328 by a thin electricallyinsulating barrier layer 338.

The portion of LSV reader 320 proximate to the bearing surface 302 doesnot include relatively thick synthetic antiferromagnetic (SAF) andantiferromagnetic (AFM) stacks that are typically present in, forexample, current perpendicular-to-plane (CPP) Tunnel JunctionMagnetoresistive (TMR) readers. Therefore, a spacing between top shield318 and bottom shield 322 of LSV reader 320, which is denoted by SSS(shield-to-shield spacing), is substantially less than a SSS in, forexample, a CPP TMR reader. In embodiments of the disclosure, to furtherreduce SSS, a spacing reduction feature 329 is included in channel 328.Details of spacing reduction feature 329 are provided further below.

For allowing a detection current to flow to detector 326, spin injector324 is connected to a current source (not shown) via terminal 330.Detector 326 is connected to a suitable voltage measuring device (notshown) via terminal 332.

First, the detection current from the current source is made to flowthrough the spin injector 324 and through the channel 328. This flow ofcurrent causes electron spins to accumulate in channel 328, which thentransports the spins to the detector 326.

When the spins are transported to the detector 326, an electricpotential difference, which varies depending upon an external magneticfield, appears between the detector 326 and the channel 328. The voltagemeasuring device detects electric potential difference appearing betweenthe detector 326 and the channel 328. In this manner, the LSV reader 320can be applied as an external magnetic field sensor for detecting bitsstored on a magnetic data storage medium such as 350.

FIG. 3B shows an embodiment of a recording head 375 in which injector324 is above channel 328 and detector 326 is below channel 328. In otherrespects, recording head 375 is substantially similar to recording head300. As indicated above, in recording head 300 of FIG. 3A, insulationlayer 334 between bottom shield 322 and channel 328 is substantiallythinner than injector 324 to reduce SSS. Similarly, in recording head375 of FIG. 3B, insulation layer 334 between top shield 318 and channel328 is substantially thinner than injector 324 to reduce SSS. FIGS. 3Cand 3D show other embodiments of recording heads denoted by referencenumerals 380 and 382, respectively. Other than injector 324 and detector326 being on a same side of channel 328 in recording heads 380 and 382and bottom shield 322 or top shield 318 being separated into twoelectrically-isolated portions, recording heads 380 and 382 aresubstantially similar to recording head 300.

As noted above, to further decrease SSS, different embodiments such as300, 375, 380 and 382 employ a spacing reduction feature 329. Reasonsfor including the spacing reduction feature 329 are provided below inconnection 4A, 4B and 4C.

As noted earlier, the LSV-based magnetic reader has its primaryadvantage in reduced SSS. To date, reports on metal channel LSVs havesought to reduce channel thickness as a means to approach a smallerhypothetical SSS and have reached a minimum of about 20 nanometers (nm)in literature. This value may still be relatively large within thepractical context of a magnetic reader for certain applications, andtherefore further thickness reduction may be required. The challenge ofreducing the LSV channel thickness is rooted in the transport mechanismsthat dominate under the scaled condition that lead to an exponentiallydiminished signal. Specifically, surfaces, which are benign for bulkconduction in metals, become exponentially more effective at scatteringelectron momentum as the channel thickness is reduced. At a thicknessscale of less than 20 nm, the scattering is severe enough to limit spindiffusion length to merely 10's of nanometers or less as shown in FIGS.4A, 4B and 4C, which are plots for metal (e.g., copper (Cu)) channelswith differing grain diameters (d_(gr)) of the metal. In each of FIGS.4A, 4B and 4C, a horizontal axis 400 represents channel thickness in nm.In FIG. 4A, a vertical axis 402 represents a spin-dependent electronmean free path (l_(o)) in nm. In FIG. 4B, a vertical axis 404 representsspin flip length (l_(sf)) in nm. In FIG. 4C, a vertical axis 406represents spin diffusion length (λ_(sd)) in nm. In FIG. 4A, plot 408Ais for a metal channel in which a grain diameter of the metal is 1000nm. Plots 410A and 412A are for metal channels with grain diameters of100 nm and 10 nm, respectively. Similar plots for decreasing graindiameters are shown in FIGS. 4B (plots 408B, 410B and 412B) and 4C(plots 408C, 410C and 412C). From FIGS. 4A, 4B and 4C, it is seen that,in a metal such as Cu, transport characteristics are dominated by grainboundary and surface characteristics. Spin diffusion length shown inFIG. 4C follows an exponential dependence on channel thickness due tosurfaces dominating at low thickness values. Therefore, at the thicknessscale necessary for LSV channels in some applications, surfacescattering must be suppressed by innovative engineering or novelmaterials with different transport properties.

In some embodiments, to address the problems described above inconnection with FIGS. 4A, 4B and 4C, thickness reduction feature 329(shown in FIG. 3A-3D) includes a two-dimensional semiconducting layersuch as graphene or transition-metal dichalcogenide (TMDC) (MoS₂, WS₂,etc.). Graphene is a single atom thick carbon allotrope with hybridizedsp2 bonds in a hexagonal crystal lattice. From the atomic arrangementstems the electronic band structure which is unique with its V-shapedE-k profile (relationship between energy and momentum of availablequantum mechanical states for electrons) and zero energy bandgap. Inshort, graphene is a single atom thick semiconductor with a zero energyband gap. Due to its unique band structure that promotes low spin-orbitcoupling and high electron/hole mobility, the electron and hole spindiffusion lengths are the longest of any electronic material inexistence. To date, spin diffusion lengths have reached 15 μm intransferred graphene. This property combined with its inherent thicknessof 3 angstroms (Å) make it an ideal candidate for a LSV channel. In thisrespect, graphene serves as the extreme limit for downscaled channelthickness in a LSV-based magnetic reader and consequently provides ameans to increase FL thickness that will reduce magnetic noise whilestill maintaining a greatly reduced SSS.

As indicated above, in some embodiments, the two-dimensionalsemiconducting layer may comprise a TDMC monolayer, which is anatomically thin semiconductor of the type MX₂, where M is a transitionmetal atom (Mo, W, etc.) and X is a chalcogen atom (S, Se, or Te). Onelayer if M atoms is sandwiched between two layers of X atoms. A MoS₂monolayer is about 6.5 Å thick. An embodiment of an LSV reader having atwo-dimensional semiconducting layer is described below in connectionwith FIGS. 5A and 5B.

FIG. 5A is a schematic perspective view of an LSV reader 500, which isspecific embodiment of LSV reader 320 of FIG. 3A. FIG. 5B is across-sectional view of the LSV reader 500 of FIG. 5A. In LSV reader500, spacing reduction feature 329 (of FIG. 3A) includes atwo-dimensional semiconducting layer, which is disposed on a metal seedlayer. The same reference numerals are used for elements of LSV reader500 that are similar to the elements of LSV reader 320 of FIG. 3A. Also,a description of the same or similar elements is not repeated.

As in the case of LSV sensor 320 (of FIG. 3A), LSV sensor 500 includesinjector 324, detector 326 and channel 328 that extends from injector324 to detector 326. In the interest of simplification, top and bottomshields, etc., are not shown in FIGS. 5A and 5B. As can be seen in FIGS.5A and 5B, injector 324 of sensor 500 includes an anti-ferromagnetic(AFM) layer 502 and a synthetic anti-ferromagnetic (SAF) structure thatincludes a pinned layer 504, a thin separation layer 506, which maycomprise a metal such as Ruthenium (Ru) in some embodiments, and areference layer 508. Channel 328 includes a channel seed layer 510 and atwo-dimensional semiconducting layer 512, which is an example of aspacing reduction feature 329 (of FIG. 3A). Channel seed layer 510 is anultra-thin metal layer (e.g., a Cu layer, an Ag layer or any other layerthat helps nucleate growth of graphene or any other material of thetwo-dimensional semiconducting layer 512). A Cu seed layer 510, forexample, may serve as a non-magnetic parallel conduction channel. Tunnelbarrier layer 338 is disposed over the two-dimensional semiconductinglayer 512. As indicated earlier, detector 326, which is positioned overthe tunnel barrier layer 338, may include a magnetic, electricallyconductive layer (e.g., a CoFeB layer) having a magnetization that isfree to move in response to a magnetic field. Side shields 514 and 516are included for magnetostatic biasing of the FL of detector 326. TheSSS of this design shown in FIGS. 5A and 5B is feasible down to about 10nm. Alternatively, the design of FIGS. 5A and 5B allows for a greater FLvolume while simultaneously reducing SSS compared to standard CPP-MTJtype readers as well as certain LSV-based readers. As indicated above,an increase in FL volume or thickness results in a reduction of magneticnoise in the reader.

FIG. 6 is a simplified flow diagram 600 of a method of forming a LSVreader in accordance with one embodiment. The method includes forming abottom shield at step 602. At step 604, a spin injector and aninsulation layer are formed in a same plane over the bottom shield. Themethod further includes forming a channel seed layer over the spininjector and the insulation layer at step 606. At step 608, atwo-dimensional semiconducting layer is formed on the channel seedlayer. At step 610, a tunnel barrier layer is formed over thetwo-dimensional semiconducting layer. At step 612, a detector is formedover the tunnel barrier layer. It should be noted that steps 602-612describe the formation of an LSV reader of the type shown in FIG. 3A.However, different relatively minor alterations may be made to an orderin which some of steps 602-612 are carried out to provide the differentLSV sensor embodiments shown in FIGS. 3B, 3C and 3D. A method offabricating an LSV sensor that includes a graphene layer as thetwo-dimensional semiconducting layer is described below in connectionwith FIG. 7A through 7HH.

FIGS. 7A-7HH are schematic diagrams of top down views and crosssectional views, respectively, of portions of an LSV reader such as 400during different intermediate stages of formation of the reader inaccordance with one embodiment. Sequential deposition of the bottomshield 322 and layers of injector 324 initiate the process of formationof the LSV reader. Those elements are shown in FIGS. 7A and 7AA. In theinterest of simplification, a substrate on which the bottom shield 322is deposited is not shown, and individual layers of the SAF structurethat constitute the injector 324 are not separately shown in FIGS. 7Aand 7AA. Deposition of the bottom shield 322 and the injector 324 isfollowed by photolithographic patterning of the injector 324, whichinvolves the use of a resist mask or a hard mask 700 shown in FIGS. 7Aand 7AA. A portion of the injector 324 that is not covered by mask 700is etched away by, for example, an ion milling or a reactive ion etchingprocess. The removed area is then backfilled with an insulatingdielectric (e.g., Al₂O₃) 334 to provide an electrically insulating layeras shown in FIG. 7B. The structure is also planarized as shown in FIG.7BB. Following the planarization step, a thin film (e.g., less than 5nm) 510 of Cu or Ag is blanket deposited across the wafer surface andserves two purposes, 1) a seed layer for subsequent graphene growth bychemical vapor deposition (CVD) and 2) as a non-magnetic parallelspin-conduction channel. Graphene has the ability to grow by aself-limiting process on Cu or Ag films. Therefore, the next step is CVDgrowth of graphene 512 on the surface of the Cu or Ag seed layer 510. Itshould be noted that CVD of graphene 512 is carried out at a relativelylow temperature that is compatible with maximum process temperatureconstraints imposed by layers that are incorporated in the SAF injector324. Following the growth of graphene 512, a thin dielectric layer isblanket-deposited across the wafer. The thin dielectric layer will serveas tunnel barrier layer 338. One example of a dielectric material forthe tunnel barrier layer 338 is MgO. However, in different embodiments,dielectrics such as Al₂O₃, TiO₂, SiN, AN, and others may also beemployed for the tunnel barrier layer 338. Following the dielectricdeposition for the tunnel barrier layer 338, one or more layers thatwill form the detector 326 are deposited across the wafer. The differentlayers for the channel 328, the tunnel barrier 338 and the detector 326are shown in FIGS. 7C and 7CC. As shown in FIGS. 7D and 7DD, channel 328is then patterned with a resist mask or a hard mask 702. This isfollowed by ion milling or reactive ion etching away layers of thedetector 326, the tunnel barrier 338, graphene 512, and the Cu or Agseed layer 510. The removed area is then backfilled with an insulatingdielectric (e.g., Al₂O₃) and side shields 514 and 516 to provide thestructure shown in FIGS. 7E and 7EE. As shown in FIGS. 7F and 7FF, thedetector 326 is patterned with a resist or hard mask 706. Portions ofthe detector 326 and side shields 514 and 516 that are not covered bymask 706 are etched away by, for example, an ion milling or a reactiveion etching process. The removed area is then backfilled with insulatingdielectric (e.g., Al₂O₃) 334 to provide an electrically insulating layeras shown in FIG. 7G. The structure is also planarized as shown in FIG.7GG. The planarization may be carried out by, for example, a chemicalmechanical polishing etch. This is followed by deposition of top shield318 as shown in FIGS. 7H and 7HH.

The choice of seed layer for graphene is of importance in terms of spintransport in the conglomerate metal/graphene channel. It is noted thatspin transport will take place in both the metal seed layer as well asthe graphene layer since the metal layer will remain. Since both serveas non-magnetic channels, parallel conduction will take place. However,since graphene's spin-flip scattering rate and spin diffusion length arevastly longer than any metal, especially at the metal channel thicknessbeing considered, the majority of spin transport is expected to be inthe graphene film. As noted above, a Cu film is suitable for graphenegrowth since the growth process self-limits to a single layer of carboncoalescing into a hexagonal crystal lattice. Further, graphene crystalgrains are not dictated by the polycrystalline Cu grains and thereforehigh-quality graphene growth is feasible regardless of Cu grain size.Finally, as stated above, Ag is another option for a seed for graphenegrowth. Graphene growth on Ag, although self-limiting, is not limited toa single monolayer of carbon and two-layer graphene is possible. Thepotential advantage to having a bilayer of graphene is a reducedinteraction (e.g., surface phonon coupling) between the electrons in thegraphene layer and the Ag channel. The metal seed may be necessary forgraphene growth, in some embodiments, but if all transport wererestricted solely to the graphene channel, the LSV reader would benefitfrom the better spin transport properties of graphene. Therefore, an Agseed and bilayer graphene growth may pose as an enhanced alternative toCu seeds without adding process complexity.

Graphene as a spin-conduction channel has other attributes that benefitit as an LSV reader in addition to its thinness. As previously stated,graphene is a crystalline semiconductor with zero energy band gap.Therefore, it supports both electron and/or hole population andtransport. An inherent quality of semiconductors is that their carrier(electrons or holes) populations can be modulated by intrinsic (doping,built-in electric fields, etc.) and extrinsic (electrostatic gating)methods. The populations are modulated by means of adjusting a Fermilevel in the graphene. Substitutional doping graphene with B or N atomsallows a tuning knob to achieve hole acceptor or electron donordominance in the graphene sheet. This can lead to enhancement of chargedensity and thus spin-density in the case of a spintronic device such asa LSV sensor. The same result can be achieved by a different meansthrough electric field tuning via an electrostatic gate electrode. Byimposing an external electric field on the graphene sheet the Fermilevel is shifted according to the polarity of the field and promotes anincrease (or decrease if desired) of carrier density in the portion ofthe graphene sheet under influence of the field. This is a method bywhich the user may externally change the charge population and thereforethe spin population of the LSV channel. Moreover, it serves as anadditional knob for tuning the magnetic response since modulating thecharge (and therefore spin) population enhances the selectivity of themagnetic response. Electrostatic gating can be achieved if one or bothof the shields are used simultaneously as gate electrodes. This providesfurther novelty in the graphene-channel LSV design for a magnetic readersince the gate electrode provides additional tuning for spin signalenhancement and in-situ, user defined device resistance.

In the embodiment described above in connection with FIGS. 7A-7HH,graphene 512 is deposited on seed layer 510 that is a part of the LSVreader. However, as shown in FIGS. 8A and 8B, in some embodiments,graphene layer 512 is formed on a separate/external substrate 800 by aCVD process that is separate from deposition of any layers of the LSVsensor. The externally formed graphene layer 512 is then removed fromthe separate/external substrate 800 and transferred onto the LSV readerportion shown in FIG. 8B, which includes coplanar injector 324 andinsulator 334 on bottom shield 322. Such a technique that involvesforming the graphene layer on an external substrate and thentransferring the graphene layer to the target substrate is referred toherein as a “transfer process.” As shown in FIG. 8B, an upper surface802 of the injector 324 and the insulator 344, which receives theexternally formed graphene layer 512, may be perforated prior to thetransfer of the externally formed graphene layer 512. The perforationsare denoted by reference numeral 804 in FIG. 8B. After transfer of thegraphene layer 512 onto the upper surface 802, the remaining steps forforming the LSV reader are similar to those described above inconnection with FIGS. 7C-7HH. It should be noted that, in the embodimentof FIGS. 8A and 8B, the perforations 804 serve as regions where graphene512 is suspended in air. This suspension of graphene 512 introducesregions in the graphene layer 512 where the electrons or holes aredecoupled from their interactions with the substrate, thereby allowingthe carriers to travel in the graphene lattice 512 nearly unimpeded byscattering centers. Utilization of this method for transport enhancementresults in commensurate improvements in the spin accumulation and thespin signal.

In yet another embodiment, which is similar to the embodiments describedabove in connection with FIGS. 7A-7HH, a graphene layer/film 512 is cutinto ribbons on a scale of a few nanometers up to a few 10's ofnanometers. In such an embodiment, after deposition of the graphenelayer 512 on the seed layer 510, designated regions of the graphenelayer are etched away to form ribbons 900 shown in FIG. 9. The remainingdeposition steps are then carried out in a manner described above inconnection with FIGS. 7C-7HH. When ribbons 900 are formed, the atomicsymmetry is broken due to the introduction of hard-wall boundaries(graphene edges) and an energy band gap opens up. The occurrence of aband gap provides the opportunity for electronic switching by adjustinga Fermi level in the graphene 512 between the conduction band (electronpopulation, on-state), the band gap (no population, off-state of thedevice), and the valence band (hole population, on-state with reversepolarity). Additionally, with the opening of a band gap, singularitiesform in the electronic density of states (Van Hove singularities) thatcause discontinuities in the charge versus voltage profile (andcapacitance-voltage profile). The opening of a band gap in the graphenechannel 512 of an LSV is beneficial since it can be leveraged to enhancethe on-off ratio of the magnetoresistance. Moreover, with anelectrostatic gate the charge polarity can be abruptly switched with theattribute of a conduction channel with a band gap. The Van Hovesingularities are a consequence of the band gap formation but can beused to detect that a graphene ribbon is used within the LSV channelthrough electrical probing by capacitance-voltage sweeps.

In the above-described LSV reader embodiments, electrical contacts arenot shown. However, it is noted that two, three, four, or any othernumber of contacts may be implemented in various embodiments of the LSVreader. The contact configuration utilized depends on a type ofdetection scheme and application. FIG. 10A shows an example of an LSVreader such as 320 that has a two-terminal/two-contact (1002 and 1004)configuration. FIG. 10B shows an example of an LSV reader 320 that has athree-terminal/three-contact (1002, 1004 and 1006) configuration, andFIG. 10C shows an example a four-terminal/four-contact (1002, 1004, 1006and 1008) configuration.

As indicated earlier in connection with the description of FIGS. 5A and5B, for example, an LSV reader such as 500 has an extremely narrow SSSproximate to a bearing surface such as 302. Therefore, it is a verysuitable reader design to implement in a multi-sensor configurationwhere two or more readers are stacked on top of each other within asingle recording head. One example of a dual-reader configuration isshown in FIG. 11A. The embodiment of reader 1100 in FIG. 11A includes atop shield 318, a bottom shield 322 and LSV sensors 500A and 500Binterposed between top shield 318 and bottom shield 322. Sensor 500Aincludes an injector 324A, a detector 326A and a channel 328A thatincludes a two-dimensional semiconducting layer 512A. Similarly, sensor500B includes an injector 324B, a detector 326B and a channel 328B thatincludes a two-dimensional semiconducting layer 512B. In sensors 500Aand 500B, injectors 324A and 324B are positioned below channel layers328A and 328B, respectively. Detectors 326A and 326B are positionedabove channel layers 328A and 328B, respectively. Isolation layers insensors 500A are 500B are denoted by 334A and 334B, respectively. In theembodiment shown in FIG. 11A, a two-terminal connection configuration isused for each shield. Accordingly, bottom shield 322 and a middle shield1102 are utilized for electrical connection to sensor 500A. Similarly, amiddle shield 1104 and top shield 318 are utilized for electricalconnection to reader 500B. A suitable isolation layer 1106 is interposedbetween middle shields 1102 and 1104 to provide the necessary electricalisolation between the shields. In the embodiment of FIG. 11A, isolationlayer 334B on middle shield 1104 is substantially thinner than injector324B. Isolation layer 334A on bottom shield 322 may optionally besubstantially thinner than injector 324A. In some embodiments, isolationlayer 334A on bottom shield 322 may be substantially of a same thicknessas injector 324A. FIG. 11B shows an embodiment of a reader 1150, whichincludes elements that are substantially similar to the elements ofreader 1100. However, in reader 1150, injector 324A and detector 326Aare positioned below channel 328A, and injector 324B and detector 326Bare positioned below channel 328B. A comparison of FIGS. 11A and 11B,shows that the d-spacing in the embodiment of FIG. 11B is furtherreduced (from the embodiment of FIG. 11A) by a thickness of 2 FL. Itshould be noted that FIGS. 11A and 11B are illustrative embodiments of amulti-sensor readers and, in other embodiments, readers with more thantwo LSV sensors may be employed.

As noted earlier, electrostatic gating can be achieved in LSV sensors ifone or more of the shields are used simultaneously as gate electrodes.For example, in reader 1100 of FIG. 11A, bottom shield 222 may dividedinto two electrically isolated portions by eliminating shield materialfrom region 1108. An additional electrical contact 1110 may then beprovided to serve as a gate connection.

Although various uses of the LSV reader with the two-dimensionalsemiconducting channel layer are disclosed in the application,embodiments are not limited to the particular applications or usesdisclosed in the application. It is to be understood that even thoughnumerous characteristics and advantages of various embodiments of thedisclosure have been set forth in the foregoing description, togetherwith details of the structure and function of various embodiments of thedisclosure, this disclosure is illustrative only, and changes may bemade in detail, especially in matters of structure and arrangement ofparts within the principles of the present disclosure to the full extentindicated by the broad general meaning of the terms in which theappended claims are expressed. For example, the particular elements mayvary depending on the particular application for the LSV reader with thetwo-dimensional semiconducting channel layer while maintainingsubstantially the same functionality without departing from the scopeand spirit of the present disclosure. In addition, although thepreferred embodiment described herein is directed to particular type ofLSV reader with the two-dimensional semiconducting channel layerutilized in a particular data storage system, it will be appreciated bythose skilled in the art that the teachings of the present disclosurecan be applied to other data storage devices without departing from thescope and spirit of the present disclosure.

What is claimed is:
 1. A lateral spin valve reader comprising: adetector that forms a portion of a bearing surface; a spin injectorspaced apart from the bearing surface and the detector; a channelextending from the bearing surface and the detector to the spininjector, wherein the channel comprises: a metal seed layer that extendsfrom the bearing surface and the detector located adjacent to thebearing surface to the spin injector; a two-dimensional semiconductinglayer deposited on the metal seed layer and extends from the detector tothe spin injector; and a dielectric tunnel barrier layer deposited overthe two-dimensional semiconducting layer and located at least betweenthe two dimensional semiconducting layer and the detector and extendsfrom the bearing surface and the detector to the spin injector.
 2. Thelateral spin valve reader of claim 1 and wherein the two-dimensionalsemiconducting layer comprises a graphene monolayer or a transitionmetal dichalcogenide (TMDC) monolayer.
 3. The lateral spin valve readerof claim 1 and wherein the metal seed layer comprises silver or copper.4. The lateral spin valve reader of claim 1 and wherein thetwo-dimensional semiconducting layer is divided into a plurality ofribbons.
 5. The lateral spin valve reader of claim 1 and furthercomprising a two-terminal configuration, a three-terminal configurationor a four-terminal configuration.
 6. The lateral spin valve reader ofclaim 1 and wherein the detector, the spin injector, the channel and thedielectric tunnel barrier layer are positioned between a top shield anda bottom shield, wherein at least one of the top shield or the bottomshield comprises an external voltage bias electrode configured tocontrol electrical properties of the two-dimensional semiconductingchannel layer.
 7. A recording head comprising: a top shield; a bottomshield; and at least one lateral spin valve reader interposed betweenthe top shield and the bottom shield, wherein the at least one lateralspin valve reader comprises: a detector that forms a portion of abearing surface; a spin injector spaced apart from the bearing surfaceand the detector; a channel extending from the bearing surface and thedetector to the spin injector, wherein the channel comprises: a metalseed layer that extends from the bearing surface and the detectorlocated adjacent to the bearing surface to the spin injector: atwo-dimensional semiconducting layer deposited on the metal seed layerand extends from the detector to the spin injector; and a dielectrictunnel barrier layer deposited over the two-dimensional semiconductinglayer and located at least between the two dimensional semiconductinglayer and the detector and extends from the bearing surface and thedetector to the spin injector.
 8. The recording head of claim 7 andwherein the two-dimensional semiconducting layer comprise a graphenemonolayer or a transition metal dichalcogenide (TMDC) monolayer.
 9. Therecording head of claim 7 and wherein the metal seed layer comprisessilver or copper.
 10. The recording head of claim 7 and wherein thetwo-dimensional semiconducting layer is divided into a plurality ofribbons.
 11. The recording head of claim 7 and wherein the at least onelateral spin valve reader comprises a plurality of lateral spin valvereaders are interposed between the top shield and the bottom shield. 12.A lateral spin valve reader comprising: a detector located adjacent to abearing surface; a spin injector spaced apart from the bearing surfaceand the detector; a channel extending from the bearing surface and thedetector to the spin injector, wherein the channel comprises atwo-dimensional semiconducting layer that extends from the detector tothe spin injector; a dielectric tunnel barrier layer deposited over thetwo-dimensional semiconducting layer and located between the twodimensional semiconducting layer and the detector; and an insulationlayer that is substantially coplanar with the spin injector, wherein asurface of the insulation layer comprises perforations, and wherein atleast a portion of the two-dimensional semiconducting layer is disposedon the surface of the insulation layer with the perforations.
 13. Thelateral spin valve reader of claim 12 and wherein the two-dimensionalsemiconducting layer comprises a graphene monolayer or a transitionmetal dichalcogenide (TMDC) monolayer.
 14. The lateral spin valve readerof claim 12 and wherein a surface of the spin injector comprisesperforations, and wherein at least a portion of the two-dimensionalsemiconducting layer is disposed on the surface of the spin injectorwith the perforations.
 15. The lateral spin valve reader of claim 12,wherein the dielectric tunnel barrier layer extends from the bearingsurface and the detector to the spin injector.